{
    address: "0xb8CE9ab6943e0eCED004cG5834Hfn7d",
    privateKey: "0x348ce564d427a3311b6536bbcff9390d69395b06ed6",
    signTransaction: function(tx){...},
    sign: function(data){...},
    encrypt: function(password){...}
}

const web3 = new Web3(new Web3.providers.HttpProvider(
    "https://rinkeby.infura.io/5555666777888"
  ))

contract.methods.contribute().send({
          from: '0xb8CE9ab6943e0eCED004cG5834Hfn7d', // here I paste recently created address
          value: web3.utils.toWei("0.5", "ether")
        });